[PATCH] rtc: efi: Fail probing if RTC reads don't work

From: Alexander Graf
Date: Sun Jun 05 2016 - 05:36:00 EST

While the EFI spec mandates an RTC, not every implementation actually adheres
to that rule (or can adhere to it - some systems just don't have an RTC).

For those, we really don't want to probe the EFI RTC driver at all, because if
we do we'd get a non-functional driver that does nothing useful but only spills
our kernel log with warnings.

Signed-off-by: Alexander Graf <agraf@xxxxxxx>
drivers/rtc/rtc-efi.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/drivers/rtc/rtc-efi.c b/drivers/rtc/rtc-efi.c
index 96d3860..0130afd 100644
--- a/drivers/rtc/rtc-efi.c
+++ b/drivers/rtc/rtc-efi.c
@@ -259,6 +259,12 @@ static const struct rtc_class_ops efi_rtc_ops = {
static int __init efi_rtc_probe(struct platform_device *dev)
struct rtc_device *rtc;
+ efi_time_t eft;
+ efi_time_cap_t cap;
+ /* First check if the RTC is usable */
+ if (efi.get_time(&eft, &cap) != EFI_SUCCESS)
+ return -ENODEV;

rtc = devm_rtc_device_register(&dev->dev, "rtc-efi", &efi_rtc_ops,